| 摘要 |
A method of forming a semiconductor structure, and a structure thereof are provided. The method is based on a novel lift-off masking process, and has particular application for forming gate structures for FETs with sputtered metals. After providing a weakly bonded surface layer on the substrate, a multilayer masking layer stack is deposited, and patterned to define an opening with undercut sidewalls. The multilayer masking stack forms a heat resistant mask for nigh temperature deposition of one or more conductive layers, e.g. sputtered metals to form a gate metal stack for a FET. The undercut sidewalls of the mask create a discontinuity in the deposited metal layers. Preferential etching of the deposited metal layers occurs at the discontinuity, resulting in separation of the gate metal structure and the excess metal overlying the masking layers. The weakly bonded surface layer on the substrate controls the adhesion of the overlying masking layers, and allows for the excess metal and the underlying masking layers to be separated from the substrate simply by a liftoff process. The latter is conveniently accomplished by application of an adhesive tape to pull up and remove the layers, separating the weakly bonded surface layer, e.g. an oxide from the substrate. The method provides for a gate structure comprising a multilayer metal stack characterized by smoothly tapered sidewalls, with substantially no undercut in which the taper angle may be controlled. Advantageously, the method avoids ion etch damage to the substrate surface surrounding the gate metal stack.
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